Webinar Series by ISPRS TC IV
Derya Akkaynak
Key role of photogrammetry in color reconstruction of underwater images
Date/Time: March 4th Friday, 3pm CET / 9am EDT
ISPRS WG IV/9 (Geovisualization, Augmented and Virtual Reality) Webinar
Speaker: Dr Derya Akkaynak (University of Haifa)
Moderator: Arzu Cöltekin, University of Applied Sciences & Arts, Northwestern Switzerland
Abstract
Consumer cameras have become commonplace in most research labs. But as we go about our research, we rarely take photos in fog. We simple wait a few hours (or days) for the fog to clear or use sensors that provide superior visibility than consumer cameras to get the information we need. Marine scientists do not have this luxury, however, because underwater, there fog is present everyday. Even in the clearest of waters, due to scattering of light from water molecules and the particles suspended in the water column, an occluding layer of ‘colored fog’ forms between the camera and the scene, and grows exponentially with distance. This curtain of colored fog reduces visibility and color contrast, hiding important visual information in the scene. Furthermore, light attenuates as an exponential function of distance underwater, resulting in the fading of colors also as a function of viewing distance. As a result, most underwater photographs are blurry, and look washed out in shades of blue or green. Key to reconstructing the contrast and ‘true’ colors of objects underwater and removing the degrading effects of water in underwater photographs, is knowing the distance to each object in the scene. The easiest and the cheapest way to object distance in an underwater scene is through photogrammetry. In this talk, I will tell you how we use photogrammetry to reconstruct colors in underwater images.
Bio
Derya Akkaynak is an aerospace engineer and oceanographer (PhD MIT & Woods Hole Oceanographic Institution ‘14) whose research focuses on problems of biological and computational vision underwater. In addition to using off-the-shelf RGB cameras for scientific imaging underwater, she also uses hyperspectral sensors to investigate how the world appears to non-human animals. Derya has professional, technical, and scientific diving certifications and has conducted underwater fieldwork in the Bering Sea, Red Sea, Antarctica, Caribbean, Northern and Southern Pacific and Atlantic, and her native Aegean. Akkaynak is an honoree for the 2019 Blavatnik Awards for Young Scientists in physics & engineering for her post-doctoral research resolving a fundamental problem in underwater computer vision — the reconstruction of lost colors and contrast — which led to the development of the Sea-thru algorithm. She is a senior lecturer at the University of Haifa, and her research lab is located at the Interuniversity Institute of Marine Sciences, in Eilat, Israel.